Nitrogen derived from human activities pollutes lakes thousands of kilometers from cities, according to new research from the University of Washington.
Researchers examined 36 lakes around the world. Three-quarters of the lakes showed traces of nitrogen from human activities before the 20th century.
Nitrogen enters the atmosphere through the use of agricultural fertilisers and burning fossil fuels. Once in the atmosphere nitrogen can be deposited as rain and snow, thousands of kilometers from its original source.Read more at University of Washington